CN106457152B - Blended membranes for water vapor transport and methods for making the same - Google Patents

Abstract

Water vapor transport membranes are provided for ERV and other water vapor transport applications. The membrane comprises a substrate and an air impermeable selective layer coated on the substrate, the selective layer comprising a cellulose derivative and a sulfonated polyaryletherketone. In certain embodiments, the sulfonated polyaryletherketone is in a cationic form and/or the selective layer comprises sPEEK and CA in a sPEEK: CA (wt.: wt.) ratio in the range of about 7:3 to 2: 3. Methods for making such membranes are provided. The method comprises applying a coating solution/dispersion to a substrate and allowing the coating solution/dispersion to dry to form a gas impermeable selective layer on the substrate, the coating solution/dispersion comprising a cellulose derivative and a sulfonated polyaryletherketone. In certain embodiments, the sulfonated polyaryletherketone is in cationic form and/or the coating solution/dispersion comprises sPEEK and CA in a sPEEK: CA (wt.: wt.) ratio in the range of about 7:3 to 2: 3.

Description

Blended membranes for water vapor transport and methods for making the same

This application claims the benefit of U.S. provisional patent application No. 62/012,533 to huzing et al, entitled "suspended polymers FOR use in the EXCHANGE AND OTHER WATER products", filed on 16.6.2014, which is assigned to the assignee of the present invention AND is incorporated herein by reference in its entirety.

FIELD

The present application relates to membranes that are selectively permeable. A particular application of the membrane according to certain embodiments is for water vapor transport. Membranes that selectively pass water vapor have applications, for example, in energy recovery ventilation ('ERV') systems.

Background

In buildings, it is often desirable to provide an exchange of air so that air from the interior of the building is exhausted and replaced with fresh air from the exterior of the building. This presents an energy cost in colder zones ('heating applications') where the interior of the building is much warmer than the outside air, or in warmer zones ('cooling applications') where the interior of the building is air conditioned and much colder than the outside air. In heating applications, the fresh air is typically cooler and drier than the air inside the building. Energy is required to heat and humidify the fresh air. In cooling applications, the fresh air is typically warmer and more humid than the air inside the building. Energy is required to cool and dehumidify the fresh air. The amount of energy required for heating and cooling applications can be reduced by transferring heat and moisture between the outgoing and incoming air. This may be accomplished using an ERV system that includes a membrane that separates the incoming and outgoing air streams. The properties of the membrane are important factors in the performance of the ERV system.

Ideally, the membranes in an ERV system should be: is air permeable such that the membrane can maintain an effective separation of the incoming and outgoing air streams; having a high thermal conductivity for efficient heat transfer between an incoming air stream and an outgoing air stream; and provides high water vapor transport for efficient moisture transfer between the incoming and outgoing air streams, but substantially blocks the passage of other gases. Achieving these characteristics typically facilitates the use of the film.

It is also desirable in addition to the above that the membrane be strong enough for commercial use, cost effective to produce, and comply with any applicable regulations. At least some jurisdictions have regulations that relate to the flammability of membranes used in ERV systems. For example, UL 94 is a standard issued by Underwriters Laboratories in the united states that relates to the flammability of plastics used for parts in equipment and devices. UL 94 provides additional classifications for films VTM-0, VTM-1, VTM-2. UL 723 is another standard promulgated by underwriters laboratories that provides testing for the surface burning characteristics of building materials.

There is a need for membranes suitable for ERV applications and/or other water vapor transport applications that address some or all of these issues.

SUMMARY

The present invention has many aspects. One aspect provides membranes having improved water vapor permeability and improved water vapor transport selectivity. Such membranes may be incorporated into ERV cores and ERV systems. Another aspect provides ERV cores and ERV systems incorporating such membranes.

In certain embodiments, a water vapor transport membrane is provided. The membrane comprises a substrate and an air impermeable selective layer coated on a first surface of the substrate, the selective layer comprising at least one cellulose derivative and at least one sulfonated polyaryletherketone. In certain embodiments, the sulfonated polyaryletherketones are in the cationic form.

In certain embodiments, the cellulose derivative is Cellulose Acetate (CA) and the sulfonated polyaryletherketone is sulfonated polyetheretherketone (sPEEK), and the selective layer comprises sPEEK to CA (wt.: wt.) ratio of sPEEK to CA in the range of about 7:3 to about 2: 3.

Another aspect of the invention provides a method for manufacturing a water vapor transport membrane for ERV applications or other applications where water vapor transport is desired.

In certain embodiments, a method comprises applying a coating solution or dispersion comprising at least one cellulose derivative and at least one sulfonated polyaryletherketone to a first surface of a substrate and allowing the coating solution to dry to form a gas impermeable selective layer on the first surface of the substrate. In certain embodiments, the sulfonated polyaryletherketones are in the cationic form.

In certain embodiments, the cellulose derivative is CA and the sulfonated polyaryletherketone is sPEEK, and the coating solution or dispersion comprises sPEEK and CA in a sPEEK: CA (wt.: wt.) ratio in a range of about 7:3 to about 2: 3.

Additional aspects and example embodiments are illustrated in the drawings and/or described in the following description.

Brief Description of Drawings

The drawings illustrate non-limiting exemplary embodiments of the invention.

Fig. 1A is a schematic diagram illustrating a membrane according to an exemplary embodiment.

Fig. 1B is a schematic diagram illustrating a membrane according to an exemplary embodiment.

Fig. 2 is a flow diagram illustrating a method for manufacturing a membrane according to certain embodiments.

Fig. 3 is an image of a surface of a sample film according to an exemplary embodiment.

Fig. 4 is a cross-sectional image of a sample film according to an exemplary embodiment.

Fig. 5 is an image of a surface of a sample film according to an exemplary embodiment.

Fig. 6 is an image of a surface of a sample film according to an exemplary embodiment.

Fig. 7 shows an image of a surface of a sample film according to an exemplary embodiment.

Fig. 8 shows a cross-sectional image of a sample film according to an exemplary embodiment.

Fig. 9 shows a cross-sectional image of a sample film according to an exemplary embodiment.

Fig. 10A is a graph showing the increase in acetic acid crossover (acetic acid cross) of the sample film as a function of relative humidity.

Fig. 10B is a graph showing the increase in ethanol crossover of the sample membrane as a function of relative humidity.

Fig. 11 is a graph showing the relationship between water vapor adsorption and relative humidity of the sample film.

Fig. 12 is a graph showing water vapor desorption versus relative humidity for a sample membrane.

FIG. 13 is a schematic diagram illustrating an ERV core according to an exemplary embodiment.

FIG. 14 is a schematic illustrating an ERV core in an ERV system according to an exemplary embodiment.

Detailed Description

Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the present invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Definition manifest

AA crosses-acetic acid.

About-means close to (i.e., within +/-20% of) the stated value.

Acetyl content-weight percentage (%) of vinyl groups in cellulose acetate.

Blend-a mixture of a substance and one or more other substances, wherein the substance and the one or more other substances combine without chemically reacting with each other.

CA-cellulose acetate. Cellulose acetate is the acetate of cellulose. Cellulose acetate is typically derived from cellulosic materials of natural origin. Cellulose acetate may be made by acetylating a cellulosic material with acetic acid and acetic anhydride in the presence of sulfuric acid. The degree of acetylation typically ranges from about 20% to about 60% (% acetyl content).

CAB-cellulose acetate butyrate.

CAP-cellulose acetate propionate.

Coating load (coating loading) or coating weight-coated on a substrate in g/m²Basis weight of the selective polymeric film layer (basis weight). When the coating is applied as a continuous dense thin film on the substrate surface, the coating weight is proportional to the thickness of the coating.

DMF-dimethylformamide.

DMSO-dimethyl sulfoxide.

DP-dry process.

Degree of DS-sulfonation. The Degree of Sulfonation (DS) refers to the sulfonic acid (SO) contained in the polymer₃H) The ratio of the PEEK monomer units of the group to the total number of PEEK monomer units in the polymer. DS ═ y/(x + y), where x is the total number of non-sulfonated PEEK monomeric units in the polymer and y is the total number of sulfonated PEEK monomeric units in the polymer. 100% DS means that each PEEK monomer unit in the polymer has a sulfonic acid group.

DP-PP-a porous polypropylene substrate made by the dry drawing process.

EATR-exhaust air delivery ratio.

EC-ethyl cellulose.

EM-electron microscopy.

ERV-energy recovery ventilation. Energy recovery ventilation is used to provide air exchange in buildings. ERVs transfer both heat and moisture between the outgoing air and the incoming fresh air. ERV is performed using an air-to-air heat exchanger that transfers both sensible and latent heat.

ERV core-a heat and moisture exchanger assembled from layers or plates of film.

IEC-ion exchange capacity.

Microporous-refers to a material having pores with a diameter of less than about 0.5 microns.

M_Nca. -number average molecular weight.

MW-molecular weight.

Na-sPEEK-the sodium ion form of sulfonated polyetheretherketone, in which the proton of the sulfonic acid group is replaced by sodium ions.

NMP-N-methyl-2-pyrrolidone.

PE-polyethylene.

% porosity-void (i.e., "empty" space in the material) and is the fraction of the volume of the void compared to the total volume of the material as a percentage between 0% and 100%.

Permeance-flux normalized by vapor pressure difference (mol m)^-2s^-1Pa^-1) Or GPU (gas transmission rate unit), where 1GPU ═ 1x 10-⁶cm³(STP)cm^-2s^-1cmHg^-1。

Permeability (permeability) -flux normalized by thickness and vapor pressure (mol-m m)^-2s^-1Pa^-1) Or Barrer, wherein 1Barrer ═ 1x 10^-10cm³(STP)cm cm^-2s^-1cmHg^-1。

PTFE-polytetrafluoroethylene.

PEEK-Poly (oxy-1, 4-phenyleneoxy-1, 4-phenylenecarbonyl-1, 4-phenylene). PEEK or 'polyetheretherketone' is a thermoplastic polymer in the polyaryletherketone family of polymers. PEEK is commercially available from different manufacturers and at a variety of molecular weights.

Porosity-the total void or open volume of the material.

PP-polypropylene.

RH-relative humidity.

Selectivity-the ratio of the permeability or permeability of one chemical species through a membrane compared to another chemical species.

SEM-scanning electron microscope.

SMS-spin-melt-spin (shoot-melt-shoot). A nonwoven fabric comprising a combination of two spunbond nonwoven fabrics combined with one meltblown nonwoven fabric is adapted for use in a layered product wherein the meltblown layer is sandwiched between spunbond layers.

Solids-with respect to a solution or dispersion, it is meant the amount of dry material remaining after substantially all of the solvent in the solution or dispersion has been distilled off (e.g., by drying) divided by the total mass of material and solvent in the solution or dispersion. For example, if a 100mg solution or dispersion is applied to a region of a substrate and, after drying, a resulting solid layer weighing 10mg remains on the substrate, the 'solids content' of the original solution or dispersion is 10mg/100mg ═ 10%.

sPEEK-sulfonated polyetheretherketone. Sulfonated polyetheretherketone is a type modified by sulfonated PEEK. The degree of sulfonation of sPEEK is typically in the range of about 20% to about 100%. PEEK polymers can be sulfonated by a variety of methods to add sulfonic acid groups to the polymer chain. The change in DS in sPEEK results in changes in the permeability, adsorption, and solvent solubility properties of the polymer.

STP-standard temperature and pressure (0 ℃, 101325 Pa).

THF-tetrahydrofuran.

VOC-volatile organic compounds.

Weight percent-wt.%. Weight percent (wt.%) refers to the mass (m) of a substance₁) Mass (m) of the whole mixture_{All are}) Is defined as the ratio of

WP-wet process.

WP-PE-a porous polyethylene substrate made by a wet formation (wet formation) and drawing process.

WVT-Water vapor transport (kg/m)²Per day or mol/m²/s)。

WVTR-water vapor transport rate.

Membrane structure

Fig. 1A shows a membrane 10 according to an exemplary embodiment. The membrane 10 includes a porous substrate 12 and a selective layer 14 on a surface 13 of the substrate 12. The membrane 10 is gas impermeable and permeable to water vapor. For ERV applications, it is preferred that the membrane 10 be much more permeable to water vapor than it is to other chemicals (e.g., volatile organic compounds). In certain embodiments, the porous substrate carries a thin surface layer of a blend of water permeable polymers on one surface of the substrate. Because the film 10 is coated on only one side, there may be a preferred orientation for the film in certain applications. However, membranes with different properties and water transport properties can be obtained by applying selective layers to both sides of the substrate. In certain alternative embodiments, the porous substrate carries a thin surface layer of a blend of water permeable polymers on both sides of the substrate.

The permeability of water vapor through the membrane 10 is affected by the pore structure and thickness of the substrate 12 and the structure, composition and thickness of the selective layer 14.

In certain embodiments, the film 10 has a thickness in the range of 10 microns to 100 microns, preferably 15 microns to 50 microns. In certain embodiments, the membrane has a thickness of less than 300 microns.

Selective layer

The selective layer 14 forms a thin but continuous and dense (i.e., substantially void-free) solid layer on the surface 13 of the substrate 12. Selective layer 14 acts as a selective barrier to the transport of air and contaminant gases, but allows water and water vapor to pass through.

For WVT applications, the selective layer 14 is preferably sufficiently flexible to allow handling, pleating, and processing of the membrane 10 to form an ERV core or other such device. For such applications, the membrane 10 is typically operated in the range of about-40 ℃ to about 100 ℃.

Selective layer 14 comprises at least one sulfonated polyaryletherketone polymer blended with at least one cellulose derivative. In certain embodiments, the at least one sulfonated polyaryletherketone polymer comprises sulfonated polyetheretherketone (sPEEK). The at least one cellulose derivative may comprise Cellulose Acetate (CA), Cellulose Acetate Propionate (CAP), Cellulose Acetate Butyrate (CAB), Ethyl Cellulose (EC), or a combination thereof, preferably CA. In certain embodiments, the selective layer 14 comprises sPEEK blended with CA.

In certain embodiments, the selective layer 14 may also include desirable additives such as one or more of the following: flame retardants, additional desiccants, zeolites, inorganic additives (e.g., silica, titania, and alumina), plasticizers, surfactants, desiccant salts, and biocides.

In certain embodiments, the cellulose derivative has an acetyl content of between about 20% and about 62%, preferably about 40%. For WVT applications, the acetyl content of CA may be between about 20% to about 62%, preferably about 40%. Generally, increasing the acetyl content of CA tends to increase its solvent resistance and glass transition temperature, while decreasing its water vapor permeability. Thus, the acetyl content of CA can be selected such that the selective layer has good transport properties for vapor separation applications (i.e., one or more of: high WVT; low contaminant crossover; and compatibility with suitable solvents for solubilizing CA and sulfonated polyaryletherketone polymers such as sPEEK).

In certain embodiments, the average M of the cellulose derivative_Nca. is about 12,000 to about 122,000. For WVT applications, average M of CA_Nca. may be about 30,000 to about 122,000, preferably about 50,000.

In certain embodiments, sulfonated polyaryletherketone polymers, such as sPEEK, have a Degree of Sulfonation (DS) in the range of from about 23% to about 100%, preferably from about 60% to about 70%. For WVT applications, the DS of sPEEK may preferably be in the range of about 60% to about 70%. Below about 60% DS, the sPEEK polymer may not be soluble in acetone/water and methanol/water solutions. Above about 70% DS, sPEEK polymers may be soluble in both acetone/water and methanol/water solutions, but casting thin, dense (i.e., substantially void free) and defect free film layers on microporous substrates can be difficult. Further, above about 70% DS, Volatile Organic Compound (VOC) crossover may be increased under high humidity conditions. At very high DS, sPEEK may be soluble in water.

In certain embodiments, the sulfonated polyaryletherketone polymers have an average M_Nca. is about 20,000 to about 180,000. Average M of sPEEK for WVT applications_Nca. may be about 20,000 to about 180,000.

In certain embodiments, the proton of the sulfonic acid group of a sulfonated polyaryletherketone, such as sPEEK, is exchanged for sodium, lithium, or another cation, as described elsewhere herein.

The selective layer 14 may be selected to have the ability to transport water vapor as well as condensate in the form of liquid water. Water transport is driven by diffusion through the selective layer 14 by a concentration gradient from the wet side of the membrane 10 to the dry side of the membrane. The thickness of the selective layer 14 affects the rate of water transport therethrough, such that a thicker selective layer will tend to have a lower rate of water transport. Therefore, it is desirable to reduce the selective layer thickness in order to increase the water delivery rate without unduly compromising the selectivity of the membrane (and the ability of the membrane to act as a barrier to air mixing).

In certain embodiments, the coating loading of the selective layer 14 on the substrate 12 is at about 0.1g/m²To about 10g/m²In the range of (1), preferably about 0.5g/m²To about 2.5g/m²Within the range of (1). In certain embodiments, the loading of the selective layer 14 on the substrate 12 is less than about 5g/m²。

In certain embodiments, the thickness of the selective layer 14 on the substrate 12 is in a range from about 0.1 microns to about 10 microns, preferably from about 0.5 microns to about 2 microns, more preferably from about 0.75 microns to about 1.25 microns. In certain embodiments, the thickness of the selective layer 14 on the substrate 12 is less than about 5 microns.

Selectivity of a material refers to the ratio of the permeability or permeation rate of one chemical species through a membrane as compared to another chemical species. For ERV applications, an important aspect of the selectivity of the membrane is the relative permeability of the desired molecules (i.e., water vapor) compared to the undesirable compounds (e.g., carbon dioxide, VOCs). Polymers with high permeability and high selectivity for water vapor are desirable for use in ERV membranes. However, materials with high permeability for one compound often have high permeability (i.e., low selectivity) for other compounds as well. Furthermore, the presence of moisture in the air stream in contact with the coated surface of the film can have a 'plasticizing' effect as water vapour is drawn into the polymer film. This may result in reduced selectivity under high humidity conditions. It is desirable to reduce this effect.

By appropriate selection of the polymer blend of the selective layer, one can vary the functional relationship between water vapor permeability and selectivity. In certain embodiments, the sulfonated polyaryletherketone/cellulose derivative coated membrane has a water vapor transmission rate of at least about 6,000GPU, preferably at least about 9,000GPU at a temperature in the range of about 50% relative humidity, about 25 ℃ to about 50 ℃ and/or the AA (or other VOC) of the sulfonated polyaryletherketone/cellulose derivative coated membrane spans less than about 1% at about 50% relative humidity, preferably less than about 70% relative humidity, less than about 3% at about 25 ℃, more preferably less than about 70% relative humidity, less than about 1% at about 25 ℃, and less than about 90% relative humidity, less than about 10% at about 25 ℃, preferably less than about 90% relative humidity, less than about 6% at about 25 ℃, more preferably less than about 90% relative humidity, less than about 3% at about 25 ℃. The selectivity of water vapor over AA or other VOCs is greater than about 100 at about 30% relative humidity, at about 25 ℃, greater than about 50 at about 50% relative humidity, at about 25 ℃, greater than about 20 at about 70% relative humidity, at 25 ℃, and greater than about 5 at about 90% relative humidity, at about 25 ℃.

The water vapor transport, permeability, and permeability and/or selectivity of the membrane may be affected by one or more of temperature, humidity, and selective layer thickness. For such membranes, at a given temperature, higher humidity can increase water vapor permeability and lower humidity can decrease water vapor permeability. Temperature can affect the permeability of the membrane by changing the rate of diffusion through the membrane, or the rate of adsorption of water vapor or other chemicals into the membrane. The relative humidity, vapor pressure, or chemical potential of water in the membrane may affect one or more of the permeability of the membrane to chemicals and/or the selectivity of the membrane. In certain embodiments, when the temperature is about 25 ℃, and/or the RH is about 50%, and/or the thickness of the selective layer is about 0.5 microns to about 2 microns, preferably about 0.75 microns to about 1.25 microns, the sulfonated polyaryletherketone/cellulose derivative coated membrane has a permeability of at least about 6,000GPU to greater than about 15,000GPU, and/or the sulfonated polyaryletherketone/cellulose derivative coated membrane has a selectivity for water vapor over AA of greater than about 20, preferably greater than 50, and/or an Acetic Acid (AA) crossover of less than about 1%. At about 70% relative humidity, the AA selectivity is greater than about 20 and the AA span is preferably less than about 3%.

By appropriate selection of the polymer blend of the selective layer one can vary the water vapour permeability and/or selectivity as a function of temperature and/or RH.

As described elsewhere herein, membranes coated with blends of sPEEK and CA exhibit improved high humidity selectivity (lower acetic acid crossover (AA crossover) measured at about 90% RH) and comparable WVT compared to sPEEK coated membranes. Furthermore, as described elsewhere herein, at the same thickness of the selective layer 14 on the substrate 12, the sPEEK/CA film exhibits a significant reduction in AA crossover and ethanol crossover at higher humidity (i.e., about 50% RH to about 90% RH) as compared to sPEEK coated films.

In certain embodiments, when the temperature is about 25 ℃, and/or the RH is about 50%, and/or the thickness of the sPEEK/CA selective layer on the substrate 12 is in the range of about 0.5 microns to about 2.5 microns, the sPEEK/CA coated membrane has a water vapor transmission rate in the range of about 6,000GPU to about 15,000GPU and/or the sPEEK/CA coated membrane has an AA span in the range of about 0% to about 2%. In certain embodiments, when the temperature is about 25 ℃, and/or the RH is about 90%, and/or the thickness of the sPEEK/CA selective layer on the substrate 12 is in the range of about 0.5 microns to about 2.5 microns, the sPEEK/CA coated membrane has a water vapor transmission rate in the range of about 6,000GPU to about 15,000GPU and/or the sPEEK/CA coated membrane has an AA span of less than about 6%. The water vapor transmission rate is similar for both sPEEK and CA membranes at about 25 ℃ and about 50 ℃, but at higher relative humidity conditions the selectivity of the sPEEK/CA membrane is improved over the sPEEK membrane.

By appropriately selecting the polymer blend of the selective layer, as described elsewhere herein, the WVT rate (WVTR) increases when the selective layer is exposed to a higher RH or to a higher temperature at the same RH.

In any of the above embodiments, the sPEEK/CA selective layer may comprise a sPEEK: CA (wt.: wt.) ratio in the range of about 1:9 to about 9:1, preferably about 7:3 to about 2:3, or may be formulated from a sPEEK/CA coating solution or dispersion in an acetone/water solvent or acetone/water/ethanol solvent comprising a sPEEK: CA (wt.: wt.) ratio in the range of about 1:9 to about 9:1, preferably having a sPEEK: CA (wt.: wt.) ratio in the range of about 2:3 to about 7:3, and/or a sPEEK: CA (wt.: wt.) ratio in the range of about 1 wt.% to about 10 wt.%, preferably about 5 wt.% by weight percent of sPEEK to CA, preferably the solvent comprises about 70/30 to about 80/20 (wt./acetone/wt./water or about 65/25/10 wt./3683. /wt.) acetone/water/ethanol.

The selective layer 14 may have any combination of the above characteristics.

Selective layer coating solution or dispersion formulations

The selective layer 14 may be applied directly to the substrate 12 by a coating rod (coating rod), a slot-die (slot-die), or similar device. In bar coating, the thickness can be controlled by bar selection, solution viscosity, and solids content in the coating solution. In die coating, the thickness can be controlled by slot size, fluid pumping rate, and solution solids content. Suitable application methods include dip coating, Mayer rod (Mayer rod), blade over roll (blade over roller coating), direct gravure (direct gravure), indirect gravure, kiss coating, die stamping, and spray coating. The wet, coated substrate is then typically passed through a dryer or oven to remove excess solvent and cause the coating to adhere to the substrate surface. Drying may be achieved, for example, by hot air drying via convection. The production of these films can be done in a continuous process on a roll-to-roll apparatus, which allows for high volume, low cost manufacturing.

The selective layer 14 may be prepared by applying a solution or dispersion comprising a sulfonated polyaryletherketone/cellulose derivative as a coating to the substrate 12. The coating may be dried until it is largely solvent free, with the sulfonated polyaryletherketone/cellulose derivative selective layer continuously covering the surface of the substrate.

Solvent systems found to dissolve both sPEEK and CA include, but are not limited to, acetone/water, THF/water, NMP/water, DMF/water, DMSO/water, preferably acetone/water, acetone/water/ethanol or another ternary solvent system. Acetone/water, or acetone/water/ethanol may be used to obtain a thin, defect-free sPEEK/CA selective layer on the substrate surface.

In certain embodiments, the sPEEK/CA coating solution or dispersion may comprise a sPEEK: CA (wt.: wt.) ratio in the range of about 7:3 to about 2:3 and/or a weight percentage of sPEEK to CA in the range of about 2.5 wt.% to about 10 wt.%, preferably 5 wt.%, and/or an acetone/water solvent preferably comprising about 70/30 to about 82/20(wt./wt.) acetone/water, or an acetone/water/ethanol solvent preferably comprising about 58/22/20 to about 65/25/10 (wt./wt.) acetone/water/ethanol or another ternary solvent system.

The acetone/water solution of sPEEK/CA has a pH of less than about 1. However, acidic pH degrades CA in solution by acidolysis. This degradation will continue even after the sPEEK/CA coating solution is dried due to the presence of acetic acid generated during hydrolysis of CA. This degradation can have an impact on the water vapor transport performance and lifetime of the membrane. To substantially eliminate CA degradation, a cationic form of sPEEK may be used, wherein the protons of the sPEEK sulfonic acid groups are exchanged for sodium ions, lithium ions or other monovalent cations (e.g. potassium ions) or divalent cations (e.g. calcium ions or magnesium ions). Preferably, sodium ions are used. Degradation of CA in sPEEK/CA coating solutions and sPEEK/CA selective layers is substantially eliminated by neutralizing/exchanging sPEEK in this manner. Furthermore, the WVT properties of the neutralized/exchanged sPEEK/CA selective layer are substantially preserved.

In certain embodiments, about 80% to about 100% of the sulfonic acid group protons of the sPEEK are exchanged for sodium cation, lithium cation, or another cation. For example, the proton of the sulfonic acid group of sPEEK can be generated by reacting NaHCO with₃Or NaOH is added dropwise to an acetone/water solution of a blend of sPEEK and cellulose derivative until the pH of the solution is between about 5 and about 6 to be exchanged for sodium ions. In certain embodiments, proton exchange to cation may be polymerized in the cellulose derivativeCompleted before the substance is added. Except for NaHCO₃Other sodium salts (e.g. Na)₂CO₃) Can be used for ion exchange. Alternatively, sPEEK may be treated with an excess NaOH solution (e.g., 0.1M NaOH), wherein the polymer is soaked in a 0.1M NaOH solution and rinsed with deionized water until the pH of the wash solution is neutral (i.e., pH is about 7), and the resulting Na-sPEEK is washed with deionized water and dried. The exchange of protons may also be accomplished after coating the substrate with sPEEK/CA and drying. In this case, a salt such as NaCl or KCl may be used as the cation source. Those skilled in the art will recognize that the protons of the sulfonic acid groups of other sulfonated polyaryletherketones may be replaced with cations as described above for sPEEK.

Substrate

The substrate 12 provides most of the mechanical support and substantially determines the operating characteristics of the membrane 10. For ERV applications, the substrate 12 preferably has the required mechanical properties to be formed into the ERV core and integrated into the ERV system. These properties may include one or more of the following: ability to maintain pleats (plat) or folds (fold); ability to be thermoformed; tear resistance; sufficiently rigid to support itself between ribs or other supports without excessive deformation; and the ability to be heat welded, vibration welded, or ultrasonically welded. These properties may be advantageous when handling, sealing and/or bonding the membrane 10 and/or when creating flow channels from the membrane 10 and/or on the membrane 10 surface when assembling the ERV core.

The substrate 12 may have a high porosity. In certain embodiments, the substrate 12 has a porosity of at least about 30%, preferably in the range of about 30% to about 80%, and/or is thin (e.g., having a thickness of less than about 250 microns) and/or is hydrophobic.

The higher porosity and lower thickness of the substrate help reduce the resistance of water and Water Vapor Transport (WVT) through the substrate portion of the membrane. High porosity and low thickness are desirable provided that the substrate should provide sufficient mechanical strength to withstand the intended operation without damage. The pore size is preferably just small enough to allow a continuous coating of polymer to be formed on the surface of the substrate.

In certain embodiments, the substrate has one or more of these features. The substrate in particular embodiments has a thickness of <250 microns, preferably in the range of about 4 microns to about 150 microns, more preferably in the range of 5 microns to 40 microns.

In certain embodiments, the average pore size of the substrate is in the range of about 5nm to about 1,000nm in the width or length direction, preferably in the range of about 5nm to about 500nm in the width or length direction.

Suitable substrates may include electrospun nanofiber layers (supported on a macroporous substrate layer). The fibers may be electrospun from the polymer solution and deposited on a carrier layer (e.g., a nonwoven). The sulfonated polyaryletherketone blend formulation may then be coated on or impregnated into the nanofiber layer using conventional coating methods (e.g., gravure or die coating). Fig. 1B shows a membrane 110 according to an exemplary embodiment. The membrane 110 includes an electrospun nanofiber layer 115 supported on a macroporous substrate layer 112. The selective layer 114 is coated on the surface 113 of the nanofiber layer 115 and may impregnate the nanofiber layer. The membrane 110 is gas impermeable and permeable to water vapor. As described elsewhere herein, selective layer 114 may comprise at least one sulfonated polyaryletherketone blended with at least one cellulose derivative. The substrate comprising the electrospun nanofiber layer may be impregnated or surface coated with a sulfonated polyaryletherketone blend, such as sPEEK blended with CA. An advantage of using a nanofiber scaffold as a basis for membrane fabrication is that selective layer 114 can be coated on a wide variety of support layers, which allows for the creation of formable membrane materials.

Suitable substrates may be polymers, such as polyolefins (e.g. Polyethylene (PE)), with desiccants or silica additives such as silica or various inorganic fillers (e.g. oxides of silicon, titanium, aluminium). In certain embodiments, the substrate comprises a uniaxially or biaxially stretched polyolefin, such as Polyethylene (PE) or polypropylene (PP). These porous polyolefins may be provided as a multilayer laminate of one polymer (PE or PP) or polymers (PP/PE/PP, etc.) or as separate films having different thicknesses. Other suitable substrates include expanded Polytetrafluoroethylene (PTFE), UHMWPE fibrous porous substrates, or other filler-supported polymeric films.

Suitable substrates may be made of microporous polyolefin materials. In certain embodiments, the microporous polyolefin substrate may be produced by a dry process or a wet process. For example, in certain embodiments, the substrate comprises a dry process polypropylene (DP-PP) battery separator. Such separators are used, for example, in certain lithium ion batteries. Such separators are commercially available and fairly inexpensive in commercial volumes.

In wet process manufactured substrates, a plasticizer-loaded polyolefin film is extruded as a gel. The plasticizer is then extracted with a solvent, leaving a polyolefin backbone film with an open pore structure. The pore structure of the polyolefin can then be further modified by stretching. In the dry process, the polyolefin is extruded as a melt, which aligns the polymer sheets; this polymer film is then annealed and then stretched orthogonally to the aligned direction to induce controlled tearing of the polymer structure, which results in a microporous structure (see, e.g., s.s. Zhang, "a review on the spacers of lithium-ion batteries," Journal of Power Sources, volume 164, phase 1, page 351-.

If the substrate is made of a highly porous material with large pores, the coating constituting the selective layer 14 will tend to penetrate the pores before drying, which results in partial or full impregnation of the substrate. This is undesirable because the impregnated substrate will tend to have greater resistance to water transport than a film comprising a thin surface coating of the selective polymer. Polymer penetration into the substrate occurs more readily in substrates that are fibrous in nature. Such substrates tend to 'wick' polymer coating solutions or dispersions and have less well-defined surface pore structures. More fibrous substrates also tend to have larger pore size distributions and larger average pore sizes, which results in more penetration of the polymer into the substrate. Thus, the substrate preferably has a high porosity but small pore size, a narrow pore size distribution, and a well-defined surface pore structure to facilitate coating of the selective layer 14 onto the substrate with little or no impregnation into the pores of the substrate.

Polyolefin substrates made using wet processes tend to have larger pore size distributions and often have larger average pore sizes. Thus, the coating comprising the selective layer 14 will tend to penetrate into the pores of the wet process polyolefin substrate, which results in a polymer impregnated substrate. Such membranes tend to have thicker selective layers and lower WVT performance.

In contrast, microporous polyolefin substrates produced using dry processes tend to have a more defined surface pore structure and a narrower pore size distribution, and can be coated with little or no impregnation of the polymer into the substrate. In contrast, cross-sectional Scanning Electron Microscope (SEM) images show that a well-defined coating layer remains on the surface of the dry-processed substrate. The use of a dry process substrate has been found to allow the manufacture of membranes comprising selective layers with lower effective thicknesses than when the same coating is cast on a wet process substrate, which allows higher WVT performance.

In addition, polyolefin substrates made using dry processes tend to have higher humidity selectivity (humidity selectivity) than wet process polyolefin substrates. For example, as described elsewhere herein, films comprising DP-PP substrates have high humidity selectivity (low acetic acid crossover (AA crossover) measured at about 90% Relative Humidity (RH) compared to films comprising WP-PE substrates or silica polyethylene (Si-PE) substrates.

Suitable substrates may comprise non-polymeric microporous materials (e.g., glass fiber based materials). As described elsewhere herein, the selective layer 14 may comprise at least one cellulose derivative and at least one sulfonated polyaryletherketone. The non-polymeric microporous substrate may be impregnated with or surface coated with a sulfonated polyaryletherketone blend to impart desirable properties to the membrane for certain applications. In certain embodiments, a self-supporting film of the sPEEK blend may be cast and laminated to a support layer.

Suitable substrates may comprise laminated layers for improving the handling properties of thin substrates. For example, a mechanical support layer, such as a nonwoven (e.g., having a low basis weight: (<100g/m²Preferably, it is<35g/m²) And high porosity spunbond, meltblown, spun-melt-spun (SMS)), which can be laminated with substrates described elsewhere herein (e.g., by heat or adhesive).

Preferably, substrate 12 is inherently flame retardant (i.e., made of one or more flame retardant materials) and/or prone to shrinkage by high temperature sources, such as open flame. These properties help the film 10 pass flammability tests (e.g., according to UL-94, UL-723). Because the substrate tends to constitute a major portion of the final film by weight, if the substrate is flame retardant, it is expected that the film itself will also be flame retardant.

In certain embodiments, substrate 12 does not promote microbial growth and/or is resistant to microbial growth.

The substrate 12 may have any combination of the above characteristics.

Additive agent

The properties of the film 10 can be further improved by incorporating additives into the selective layer for specific end use applications, as described in U.S. patent application No. 13/321,016 (published as US2012/0061045), which is hereby incorporated by reference in its entirety. Additives include, but are not limited to, flame retardants, desiccants, zeolites, inorganic additives (e.g., silica, titania, and alumina), plasticizers, surfactants, desiccant salts, and biocides.

Manufacturing method

Fig. 2 illustrates a method 20 for making a membrane. In block 21, a suitable substrate is provided. The substrate may, for example, be as described above. In certain embodiments, the substrate is a dry or wet process polypropylene or polyethylene substrate. In optional block 22, a substrate is prepared to receive the selective layer 14. Block 22 may, for example, include corona treatment of the substrate.

In block 23, a solution or dispersion is prepared for creating the selective layer. The solution or dispersion comprises at least one sulfonated polyaryletherketone polymer (e.g., sPEEK) blended with at least one cellulose derivative (e.g., CA) and optionally comprises other additives as described elsewhere herein.

In exemplary embodiments, the weight percentage of sulfonated polyaryletherketone polymer/cellulose derivative comprising the solution or dispersion used to form the selective layer is in the range of about 1 wt.% to about 10 wt.%, preferably about 5 wt.%. The use of solutions or dispersions having a lower weight percentage of sulfonated polyaryletherketone polymer/cellulose derivative results in thinner coating layers.

In block 24, the solution or dispersion prepared in block 23 is applied to a substrate to produce a selective layer. Without being limited to a particular method, the application may include, for example, gravure coating, metering rod coating, roll coating, die coating, or spray coating. Die coating is preferred to provide a thin, uniform coating on the substrate surface.

In block 25, the selective layer is dried (i.e., physically cured). After drying, a continuous, dense film layer of sulfonated polyaryletherketone polymer/cellulose derivative covers the substrate surface. The dense layer is substantially free of pores. In certain embodiments, the thickness of the selective layer is in the range of about 0.1 microns to about 10 microns (e.g., about 0.1 g/m)²To about 10g/m²Coating weight of).

The selective layer may be dried in air. In certain embodiments, the coated substrate may be dried in air at a temperature of about 20 ℃ to about 90 ℃. Drying may be accelerated by heating the coated substrate. For example, in other embodiments, drying occurs in a heated convection oven, in a roll-to-roll process. In such embodiments, the drying of the selective layer may be completed in about 30 seconds or less.

In a method according to an exemplary embodiment, the film 10 is prepared by applying a film comprising a sPEEK/CA dispersion to a DP-PP substrate 12. The film was allowed to dry. The sPEEK/CA selective layer continuously covers the surface of the substrate.

Pore formation at phase transition

In the current process, depending on the conditions, the solvent may begin to evaporate quickly after the selective layer coating solution/dispersion is applied to the substrate 12. Solvents with higher vapor pressure may evaporate faster than higher boiling solvents. Because the selective layer comprises a blend of two polymers with different levels of solubility in the selected solvent, there is a possibility of 'phase inversion' in the selective layer. For example, phase transformations may occur in acetone-water solutions of sPEEK/CA due to rapid evaporation of acetone and insolubility of CA in water.

Phase transitions occur when polymer rich and polymer poor phases develop in the coating layer during drying. For example, in an acetone/water/CA system, CA is more soluble in acetone (solvent) than in water (non-solvent) and acetone evaporates from the coating layer at a higher rate than water. During drying, the coating layer separates into a polymer-rich phase and a polymer-poor phase, the polymer-rich phase solidifies before the polymer-poor phase and the polymer-poor phase forms pores in the polymer-rich phase. When fully dried, the pores remain throughout the film layer. In the acetone/water/sPEEK/CA system, sPEEK is more soluble than CA in lower acetone/water ratios. During drying, when the acetone evaporates, the sPEEK remains in solution longer and thus pores are less likely to form when sufficient sPEEK is present.

Pore formation by phase transformation is generally undesirable in preparing the membrane 10. Porous phase transition membranes and layers tend to be brittle, brittle and, due to their pore structure and high number of interphase (interphase), are prone to fracture and break upon compression, bending, folding, or handling, which makes handling and/or pleating the membrane into an exchanger module problematic.

In addition, the selective layer 14 should be dense (i.e., substantially void-free) and non-porous to provide selective transport of water vapor compared to other gases and VOCs. In contrast, phase change films tend to be porous. Phase transitions may be reduced or avoided by altering one or more of the following: solvent ratio, polymer solids content, polymer ratio, drying rate, and/or film thickness. For example, void formation by phase transition is greater when the solids content of the coating is lower.

The addition of other solvents and/or non-solvents to the system may also affect pore formation through phase transition. For example, CA is insoluble in ethanol or water, but ethanol is a non-solvent that is more volatile than water. By adding ethanol to the acetone/water/sPEEK/CA system, pore formation by phase inversion is reduced. For example, when the total wt.% of ethanol in the system is greater than about 10 wt.%, preferably greater than about 15 wt.%, a reduction in pore formation by phase transformation is observed.

For membranes comprising sPEEK/CA selective layers with sPEEK: CA ratios in the range of about 2:3 to about 1:0 (solids content of the coating solution in the range of about 70/30 to about 80/20(wt./wt.) acetone/water in the range of about 4 wt.% to about 10 wt.%), no significant porosity due to phase transformation was observed on the microporous DP-PP substrate for selective layers up to 2 microns in thickness. For sPEEK/CA films where the sPEEK: CA ratio is in the range of about 2:3 to about 1:0 (from the case of acetone/water systems), no significant porosity due to phase inversion is observed. In contrast, when cast from an acetone/water system, voids are clearly observed on the surface and everywhere of sPEEK/CA films having sPEEK: CA ratios less than 1:2 (e.g., 1:3) due to phase inversion. Fig. 3 and 4 show surface and cross-sectional images, respectively, of an unsupported sPEEK/CA film cast from 80/20(wt./wt.) acetone/water, where the sPEEK: CA ratio is 1: 2. In membranes comprising sPEEK/CA selective layers wherein the solids content formulation of the selective layer is less than about 3% in 80/20(wt./wt.) acetone/water, complex pore structures at the sPEEK/CA membrane surface and throughout are also clearly observed. Figure 5 shows an Electron Microscopy (EM) image of the surface of a membrane comprising a sPEEK: CA selective layer cast on DP-PP and having a sPEEK: CA ratio of 1:1 cast from a 2.5% solids formulation in 80/20(wt./wt.) acetone/water. The observed pore structure is believed to have been produced by phase transformation. Simple bending, folding and pleating tests cause such phase transition induced porous membrane rupture, which results in increased air cross-over. Under EM, films with 'smooth' film layer surfaces do not show evidence of surface or through porosity, or porosity formed by phase transformation. These films can be bent, folded and pleated without exhibiting an increase in air crossover.

Polymer-polymer phase separation in thin films

Polymer blends, particularly those that are incompatible and cannot be fully dispersed at the molecular level, may tend to thermodynamically separate into 'phase separated' solid regions containing the individual polymer components to reduce or minimize free energy in the film layer. This may occur during drying/solvent evaporation and/or during heat treatment. These nonporous, phase separated film layers can have both positive and negative effects on the overall performance properties of the film.

In the selective layer 14, some degree of polymer-polymer phase separation of the sPEEK/CA selective layer is often desirable. For example, regions of CA (having lower swelling in the presence of water) may limit higher swollen sPEEK regions, prevent excessive dimensional instability of the selective layer in the presence of higher RH, and reduce the permeability of the selective layer to VOCs and other gases in the presence of high RH. When pore formation is substantially avoided, polymer-polymer phase separation may also be beneficial to prevent mechanical failure of the selective layer due to extreme swelling and shrinkage of the sPEEK under varying RH conditions and in the presence of liquid water condensation. Furthermore, the well-defined regions of sPEEK (having higher water vapor permeability) may allow for higher localized WVT (i.e., the well-defined regions of the polymer comprising sulfonic acid groups may improve water vapor transport).

Blending polymers in different ratios will result in different levels or morphologies of phase separation. Membranes comprising sPEEK/CA selective layers formulated from sPEEK/CA coating solutions having sPEEK: CA (wt./wt.) ratios in the range of about 7:3 to about 2:3 exhibit sPEEK and CA polymer-polymer phase separation without pore formation (fig. 6-9). FIG. 6 shows a 2:1(wt.: wt.) sPEEK: CA film surface with polymer-polymer phase separation induced morphology. No pores were seen in the film surface. Figure 7 shows a DP-PP substrate coated with an approximately 1 micron film of 1:1(wt.: wt.) sPEEK: CA coating solution (5 wt.% polymer solids in 72/28 acetone/water solution). The coating morphology suggests that a clear polymer phase is formed, but no pores. FIGS. 8 and 9 show cross-sections of films cast from acetone/water from 1:1(wt.: wt.) sPEEK: CA and 2:3(wt.: wt.) sPEEK: CA formulations, respectively. These films do not exhibit phase transformation induced porosity (as observed for the 1:2(wt.: wt.) sPEEK: CA films shown in fig. 4); however, polymer-polymer phase separation can be observed in the film morphology shown in fig. 8 and 9. For membranes comprising sPEEK: CA selective layers formulated from sPEEK/CA coating solutions having a sPEEK: CA (wt./wt.) ratio in the range of about 7:3 to about 2:3 (greater than about 3 wt.% solids in acetone/water), no phase inversion (i.e., pore formation) was observed, but polymer-polymer phase separation was visible in the film morphology.

The invention is illustrated by the following non-limiting examples.

EXAMPLE 1 sulfonation of PEEK

Seven samples of sulfonated PEEK with different degrees of sulfonation were derived from sulfonation

(MW 34,000) of PEEK. Sulfonation was performed by dissolving 30g of PEEK in 500mL of sulfuric acid (95-98 wt.%, Sigma Aldrich) according to the procedure described in the following: shibuya and R.S.Porter, "Kinetics of PEEKKULFOTION in centralized sulfuric acid," Macromolecules, Vol.25, No. 24, pp.6495-. Seven such solutions were vigorously stirred at room temperature for 96h, 120h, 144h, 172h, 192h, 264h, and 336h, respectively. At the completion of the reaction time, the mixture was precipitated in water and washed until pH>5. The sulfonated polymer was dried in an oven at 50 ℃ for at least 24 h. By titration as described in the followingDetermination of the corresponding Ion Exchange Capacity (IEC) and Degree of Sulfonation (DS): m.h.d.othman, a.f.ismail, and a.mustafa, malaysian polymer Journal,2007,2, 10-28. The results are shown in table 1.

TABLE 1

The DS ranges from about 23% to about 90%, depending on the reaction time. For formulation and coating considerations as well as swelling and performance considerations, a DS in the range of from about 60% to about 70% has generally been found to be preferred for the WVT applications described herein.

Example 2-preparation and testing of films with Si-PE substrates coated with various blends of sPEEK and CA

Silica polyethylene (Si-PE) composite (silica supported polyethylene substrate SP400 from PPG) was used as microporous substrate and the microporous substrate was prepared by using sPEEK (DS 63%) or CA (39.7% acetyl content, average M)_Nca.50,000) or blends thereof coated substrates eleven supported film samples were prepared. The properties of the resulting films were tested to determine the effect of increasing the proportion of CA in the blended polymer. Sample 2A was coated with sPEEK only and was prepared by applying a thin coating of sPEEK solution (1 g of sPEEK in acetone/water, 10% solids) to one surface of a Si-PE substrate using a Mayer rod coater (the coating process used in all examples is described in more detail herein). Sample 2K was coated with CA only and was prepared by applying a thin coating of CA solution (1 g of CA in acetone/water, 10% solids) to one surface of a Si-PE substrate using a mayer rod coater. In samples 2B-2J, the substrate was coated with a blend of sPEEK and CA; the weight percent of CA in the polymer blend was increased by samples 2B-2J in 10% increments. The membrane preparation method was essentially the same for all samples 2A-2K and the% solids in acetone/water solution was 10% in each case. For example, for sample 2F, 0.5g of CA and 0.5g of sPEEK (DS 63%) (10% solids, 5% CA, 5% sPEEK) in acetone/water were mixed together at room temperature until mixed togetherUntil a clear solution is obtained. A thin coating of CA/sPEEK solution was applied to one surface of the Si-PE substrate using a mayer rod coater. For each film sample, using the techniques described herein, the coating load was determined and the films were tested for air crossover, Exhaust Air Transport Ratio (EATR), water crossover (WVTR), and acetic acid crossover (AA crossover). The results are shown in table 2.

TABLE 2(Si-PE substrate)

^*From acetone/water (8/2) solution, 10% solids

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

n/a indicates not measured

The air cross-over was zero for all samples 2A-K, indicating that the coating formed a continuous layer or a dense thin film on the substrate. EATR was zero for all film samples except sample 2K, which was coated with only CA and had defects therein. Even though the WVTR of the film with 100% CA coating was lower than the film with 100% sPEEK coating at similar loading (22.4 kg/m)²The weight ratio of each day is 25.3kg/m²Day), it can also be seen that the addition of CA to the coating does not adversely affect WVTR, even as much as about 60% by weight CA in the blend. As shown in table 2, AA was low across all of the coated film samples under dry conditions (RH 0%). However, under high humidity conditions (RH 90%), AA crossover increased significantly. Without being bound by any theory, this is believed to be due to plasticization of the film coating polymer by water vapor. These Si-PE based film samples did not pass the UL-94HB (horizontal burn) flame color test described herein.

Example 3-preparation and testing of films with WP-PE substrates coated with various blends of sPEEK and CA

This example is similar to example 2 except that WP-PE is used as the substrate. By using sPEEK (DS 63%) or CA (39.7% acetyl content, average M)_Nca.50,000) or blends thereof was coated on a WP-PE substrate to prepare eleven supported film samples and the properties of the resulting films were tested to determine the effect of increasing the proportion of CA in the blended polymer. Sample 3A was coated with sPEEK only and was prepared by applying a thin coating of sPEEK solution (1 g of sPEEK in acetone/water, 10% solids) to one surface of the substrate using a mayer rod coater. Sample 3K was coated with CA only and was prepared by applying a thin coating of CA solution (1 g of CA in acetone/water, 10% solids) to one surface of the substrate using a mayer rod coater. In samples 3B-3J, the substrate was coated with a blend of sPEEK and CA; the weight percent of CA in the polymer blend was increased by samples 3B-3J in 10% increments. The membrane preparation method was essentially the same for all samples 3A-3K, and the% solids in acetone/water solution was 10% in each case. For example, for sample 3F, 0.5g of CA and 0.5g of sPEEK (DS 63%) (10% solids, 5% CA, 5% sPEEK) in acetone/water were mixed together at room temperature until a clear solution was obtained. A thin coating of the CA/sPEEK solution was applied to one surface of the WP-PE substrate using a Mayer rod coater. For each film sample, using the techniques described herein, the coating load was determined and the films were tested for air crossover, Exhaust Air Transport Ratio (EATR), water crossover (WVTR), and acetic acid crossover (AA crossover). The results are shown in table 3.

TABLE 3(WP-PE substrate)

^*From acetone/water solution, 10% solids

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

n/a indicates not measured

Air crossover and EATR were zero for all samples 2A-K indicating that the coating formed a continuous layer or dense film on the substrate. Even though the WVTR of the film with 100% CA coating was lower than the film with 100% sPEEK coating (16.5 kg/m)²The weight ratio of each day is 30.2kg/m²Day), it can also be seen that the addition of CA to the coating does not adversely affect WVTR, even as much as about 60% by weight CA in the blend. In fact, surprisingly, it appears that WVTR is higher for certain blends than for sPEEK alone, even when the coating load is higher (e.g., samples 3C, 3E, and 3F). The crossover of Acetic Acid (AA) increased significantly under high humidity conditions (RH 90%), again, probably due to plasticization of the film coating polymer by water vapor. However, this effect is lower for some films with blended coatings (3G-J). The effect of this improved high humidity selectivity is more pronounced for DP-PP substrates with thin film coating polymers (see example 10 herein). These WP-PP based film samples also passed the UL-94HB (horizontal burn) flame color test described herein.

Example 4-preparation and testing of films with WP-PE substrates coated with various blends of sPEEK and CA at various solids contents

In this example, the percent solids in the coating solution was varied. As in example 3, the average M was determined by using sPEEK (DS 63%) and CA (39.7% acetyl content) in an acetone/water solution_Nca.50,000) 50/50 by weight blend was coated on a WP-PE substrate to prepare four supported film samples. For sample 4A, the solution was 8% solids (0.4g sPEEK,0.4g CA), for sample 4B, the solution was 7% solids (0.35g sPEEK,0.35g CA), for sample 4C, the solution was 6% solids (0.3g sPEEK,0.3g CA), and for sample 4D, the solution was 5% solids (0.25g sPEEK,0.25 gCA). The properties of the resulting films were tested to determine the effect of varying the solids content in the coating solution. For each film sample, using the techniques described herein, the coating load was determined and the films were tested for air crossover, Exhaust Air Transport Ratio (EATR), water crossover (WVTR), and acetic acid crossover (AA crossover). The results are shown in table 4 and compared with the results for example 3, sample 3F, where the solids content is 10%.

TABLE 4(WP-PE substrate)

^*50/50 parts by weight of sPEEK/CA in acetone/water solution

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

n/a indicates not measured

The air cross-over is zero for each of samples 4A-D. When the percent solids content is reduced, the coating load tends to decrease, which results in an increase in WVTR. However, it appears that reducing the coating weight (and thickness) does not result in any increase in acetic acid crossover.

Example 5-preparation and testing of films with WP-PE substrates coated with various blends of sPEEK and CAP

This example is similar to example 3 except that Cellulose Acetate Propionate (CAP) (average M) is used in the polymer coating blend_Nca.25,000 by GPC, about 2.5% acetyl content, about 2.6 wt.% hydroxyl, about 45 wt.% propionyl, from Sigma Aldrich) instead of CA. Four supported film samples were prepared by coating a WP-PE substrate with CAP or a blend of CAP and sPEEK (DS 63%), and the properties of the resulting films were tested to determine the effect of increasing the proportion of CAP in the blended polymer. Sample 5A was prepared by attempting to apply a thin coating of sPEEK/CAP solution (0.5g sPEEK and 0.5g CAP, 10% solids in 9/1 acetone/water) to one surface of a substrate using a mayer rod coater; however, the blend separates into two phases and cannot be used as a coating with this solvent system. Sample 5B was prepared by similarly applying a thin coating of sPEEK/CAP solution (0.3g of sPEEK and 0.7g of CAP in acetone/water, 10% solids). Sample 5C was prepared by similarly applying a thin coating of sPEEK/CAP solution (0.2 g of sPEEK and 0.8g of CAP in acetone/water, 10% solids). Sample 5D was prepared by similarly applying a thin coating of CAP solution (1 g of CAP in acetone/water, 10% solids). For each film sample, the coating load was determined using the techniques described herein, and the films were tested for air cross over, Exhaust Air Transport Ratio (EATR), water crossover (WVTR). Acetic acid crossover (AA crossover) was not tested because the membranes all had defects. The results are shown in Table 5, and are comparable theretoThe results of example 3, sample 3A, with the middle coating being 100% sPEEK, were compared.

TABLE 5(WP-PE substrate)

^*In acetone/water solution

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

n/a: for sample 5A, the blend separated into two phases and could not be used as a coating with this solvent system.

With CAP/sPEEK polymers, there are difficulties in creating blend solutions and blend films. The films with sufficiently low defects to be tested had much lower WVTR than sPEEK coatings alone, indicating that the blends of sPEEK and CAP do not perform as well as the blends of sPEEK and CA. This indicates that the addition of CAP adversely affects the membrane properties, unlike the addition of CA.

Example 6-preparation and testing of films with WP-PE substrates coated with various blends of sPEEK and CAB

This example is similar to examples 3 and 5 except that Cellulose Acetate Butyrate (CAB) is used in the polymer coating blend instead of CA or CAP. By using CAB (average M)_Nca.70,000 six supported film samples were prepared by coating a WP-PE substrate by GPC, 12-15% acetyl content, 1.2-2.2 wt.% hydroxyl, 35-39 wt.% propionyl from Sigma Aldrich) or a blend of CAB and sPEEK (DS 63%), and the properties of the resulting films were tested to determine the effect of increasing the proportion of CAB in the blended polymer. Sample 6A was prepared by attempting to apply a thin coating of sPEEK/CAB solution (0.9g sPEEK and 0.1g CAB, 10% solids in 9/1 acetone/water) to one surface of a substrate using a mayer rod coater. Sample 6B was prepared by attempting to apply a thin coating of sPEEK/CAB solution (0.7 g of sPEEK and 0.3g of CAP in acetone/water, 10% solids). Sample 6C was prepared by attempting to apply a thin coating of sPEEK/CAB solution (0.5g sPEEK and 0.5g CAB, 10% solids in acetone/water). In thatIn all three cases (samples 6A, 6B and 6C), the blend separated into two phases and could not be used as a coating with this solvent system. Sample 6D was prepared by applying a thin coating of sPEEK/CAB solution (0.3g of sPEEK and 0.7g of CAB in acetone/water, 10% solids). Sample 6E was prepared by applying a thin coating of sPEEK/CAB solution (0.2 g of sPEEK and 0.8g of CAB in acetone/water, 10% solids). Sample 6F was prepared by applying a thin coating of CAB solution (1 g CAB in acetone/water, 10% solids). For each film sample, the coating load was determined using the techniques described herein, and the films were tested for air cross over, Exhaust Air Transport Ratio (EATR), water crossover (WVTR). Acetic acid crossover (AA crossover) was not tested because the membranes all had defects. The results are shown in table 6 and compared with the results for example 3, sample 3A, where the coating is 100% sPEEK.

TABLE 6(WP-PE substrate)

^*In acetone/water solution

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

n/a: the blend separates into two phases and cannot be used as a coating with this solvent system.

Similar to blends of sPEEK and CAP, WVTR performance is significantly adversely affected by the presence of CAB polymer in the coating. CAB also has compatibility issues because it is immiscible with sPEEK polymers in acetone/water formulations.

Example 7-preparation and testing of films with WP-PE substrates coated with blends of sPEEK and EC

This example is similar to example 3, example 5, and example 6 except that Ethylcellulose (EC) is used in place of CA, CAP, or CAB in the polymer coating blend. Four supported film samples were prepared by coating the WP-PE substrate with EC (48.0-49.5% (w/w) hydroxyethyl base, from Sigma Aldrich) at three different solids contents for the coating solution and for the 50/50 blend of EC with sPEEK (DS 85%), and the properties of the resulting films were tested to determine the effect of adding EC to sPEEK as a blended polymer. Since EC is insoluble in acetone/water, sPEEK with DS 85% was used for dissolution purposes in ethanol/water. Sample 7A was prepared by applying a thin coating of sPEEK/EC solution (0.5g sPEEK and 0.5g EC in 9/1 ethanol/water, 10% solids) to one surface of a substrate using a mayer rod coater. Samples 7B-D were prepared by similarly applying thin coatings of EC solutions in ethanol at 10%, 7%, and 5% solids, respectively. For each film sample, the coating load was determined using the techniques described herein, and the films were tested for air cross over, Exhaust Air Transport Ratio (EATR), water crossover (WVTR). The results are shown in table 7 and compared with the results for example 3, sample 3A, where the coating is 100% sPEEK (DS 63%).

TABLE 7(WP-PE substrate)

^*In 80/20 (wt.) acetone/water solution

^**In 90/10 (wt.) ethanol/water solution

^***In pure ethanol solution

^****Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

The water transport properties of the membrane comprising a blend of sPEEK and EC were not improved when compared to membranes comprising sPEEK or EC coatings. Reducing the solids content of the EC solution results in reduced coating loads and a corresponding increase in water delivery. Sample 7D had defects and hence EATR was produced.

Example 8-having a coating

Preparation and testing of films of WP-PE substrates with various blends of EC

This example is similar to example 7 except that the polymer coating is blendedIn the article

(DupontDE2021, sulfonated tetrafluoroethylene based fluoropolymer-copolymer) instead of sPEEK. By using

Or EC and

the blend of (a) was coated on a WP-PE substrate to prepare four supported film samples and the properties of the resulting films were tested to determine the effect of increasing the proportion of EC in the blended coating polymer. Sample 8A was prepared by using a Mayer rod coater

A thin coating of solution (20% in propanol) was applied to one surface of the substrate. Sample 8B by application

EC solution (0.5g of EC (48-49.6% ethyl basis) and 0.5g of

In ethanol, 10% solids). Sample 8C by application

EC solution (0.8g of EC (48-49.6% ethyl basis) and 0.2g of

In ethanol, 10% solids). Sample 8D by application

EC solution (0.9g of EC (48-49.6% ethyl basis) and 0.1g of

In the second placeAlcohol, 10% solids) was prepared. For each film sample, the coating load was determined using the techniques described herein, and the films were tested for air cross over, Exhaust Air Transport Ratio (EATR), water crossover (WVTR). The results are shown in table 8 and compared to the results for example 7, sample 7B, where the coating was 100% EC.

TABLE 8(WP-PE substrate)

^*Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

When and comprise

Or EC coating, including

The water transport properties of the membrane of the blend with EC were not significantly improved.

Has high water vapor permeability; however,

are expensive compared to sPEEK and exhibit reduced selectivity at higher relative humidity conditions.

Example 9-preparation and testing of films with DP-PP substrates coated with various blends of sPEEK and CA

This example is similar to example 3 except that a dry stretched processed polypropylene substrate (DP-PP) is used. Significant performance enhancement was observed with this substrate compared to the other substrates tested. This is associated with a clearly observable coating layer remaining on the surface of the film. In the previous tests, the coated surface layer could not be easily observed. While not being bound to any particular theory, it is claimed that the pore size and morphology of the substrate affects whether the coating film is deposited on the surface of the substrate, or whether it impregnates into the pores of the substrate.

In the WP-PE substrates used in examples 3-8, the surface pore structure is less well defined, has a wider pore size distribution, and the structure is more fibrous in nature, which allows the polymer in the coating solution to penetrate to a greater extent into the substrate during the coating process. With DP-PP substrates, the surface pore structure is clearly defined, there tends to be a smaller average pore size, the pore size distribution is narrower, and when coated with a polymer coating, a continuous surface film results. This is clearly visible in the cross-sectional image observed by the electron microscope. A well-defined surface film was not visible in the coated WP-PE substrate. The coating layer on the surface of the DP-PP substrate can be visually observed as a 'glossy' or smooth film on the substrate surface, as opposed to a more 'matte' or rough-surfaced coating on the surface of the WP-PE substrate.

The bare DP-PP substrate was tested for water transmission (WVTR) (see sample 9A in table 9). Seven supported film samples were prepared by coating a DP-PP substrate with sPEEK (DS 63%) or CA (as in example 3) or blends thereof and the properties of the resulting films were tested to determine the effect of increasing the proportion of CA in the blended polymer. Sample 9B was coated with sPEEK only and was prepared by applying a thin coating of sPEEK solution (10% sPEEK in acetone/water) to one surface of the substrate using a mayer rod coater. Sample 9H was coated with CA only and was prepared by applying a thin coating of CA solution (10% CA in acetone/water) to one surface of the substrate using a mayer rod coater. In samples 9C-9H, the substrate was coated with a blend of sPEEK and CA; the weight percent of CA in the polymer blend was increased by samples 9C-9H in 10% increments. The membrane preparation method was essentially the same for all samples 9C-9H, and the% solids in acetone/water solution was 10% in each case. For each film sample, the coating load was determined and the film was tested for water penetration (WVTR) using the techniques described herein.

TABLE 9(DP-PP substrate)

^*From acetone/water solution, 10% solids

^**Dynamic WVT test, 33cm²Area, 6,000cm³Flow rate per min, 50% RH in feed

Even at 50% CA/50% sPEEK, the performance of the blend film is significantly higher than would be expected from a straightforward "rule of mixing" calculation. Without being bound to any particular theory, it is believed that blending CA with sPEEK results in a change in the morphology of the coating layer, possibly due to phase separation upon drying, which may improve the permeability of the coating layer. Furthermore, CA blended in sPEEK appears to reduce swelling of sPEEK in coating layers without significantly reducing the water vapor transmission rate of the coating. An additional benefit is that these DP-PP substrate based film samples also pass the UL-94HB (horizontal burn) flame color test described herein.

Example 10 contaminant crossover under varying RH conditions for DP-PP substrates coated with various blends of sPEEK and CA

The apparatus was developed to allow for controlled humidity on both sides of the membrane sample while allowing for controlled generation of contaminants in the feed stream to the apparatus. Crossover of acetic acid and ethanol was determined for 3 different coated film samples at room temperature (23.3 ℃) at RH ranging from 0% to 90% using DP-PP as substrate. Sample DP-PP-sPEEK was coated with sPEEK (DS 63%) and prepared by applying a thin coating of sPEEK solution (1 g of sPEEK in acetone/water, 10% solids) to one surface of a DP-PP substrate using a mayer rod coater. Sample DP-PP-CA was coated with CA (39.7% acetyl content, average M)_Nca.50,000) and was prepared by applying a thin coating of CA solution (1 g of CA in acetone/water, 10% solids) to one surface of a DP-PP substrate using a mayer rod coater. In sample DP-PP-sPEEK-CA, the DP-PP substrate was coated with a blend of sPEEK and CA in a1:1 ratio (0.5g of CA and 0.5g of sPEEE in acetone/water)K (DS 63%) (10% solids, 5% CA, 5% sPEEK) was mixed together at room temperature until a clear solution was obtained). The coating process is accomplished using a mayer rod coater. All three film samples had approximately the same polymer loading and coating thickness. The results of the contaminant crossing test are shown in table 10, and are also plotted in the graphs shown in fig. 10A and 10B.

Watch 10(DP-PP base)

^*ASTM F-739 Module (5 cm)²Area), 600cm³Flow rate per min, 100-400ppm VOC

Increasing RH in the contaminant stream generally increases VOC (especially acetic acid and ethanol) crossover. Without being bound to any particular theory, this is believed to be due to plasticization of the film coating polymer by water vapor. As previously observed, for the membrane coated with sPEEK only (sample DP-PP-sPEEK), the contaminant crossover increased significantly at high RH (e.g. above 50% for AA and 90% for ethanol). However, the membrane coated with a1:1 blend of sPEEK: CA (sample DP-PP-sPEEK-CA) showed significantly lower contaminant crossover at high RH than the DP-PP-sPEEK sample-results closer to the sample with CA-only coating (DP-PP-CA).

Using the techniques described herein, each of the three example 10 film samples was tested for WVT properties at 50% RH at two different temperatures. The results are reported in table 11.

TABLE 11(DP-PP substrate)

^*ASTM F-739 Module (5 cm)²Area), 600cm³Flow rate per min

^**Dynamic WVT test, 33cm²Area, 6000cm³Flow rate per min

The sample coated with the 1:1 blend of sPEEK: CA (sample DP-PP-sPEEK/CA) exhibited significantly higher WVTR at both temperatures than the sample with the CA coating alone (DP-PP-CA). The WVTR value of the sample with the blended coating (sample DP-PP-sPEEK/CA) is closer to the WVTR value of the sample with the sPEEK coating (DP-PP-sPEEK).

Data showing water vapor transmission rates and selectivity for water vapor transport compared to acetic acid and ethanol transport are reported in tables 12 and 13 at different Relative Humidities (RH) for each of the three example 10 film samples. Selectivity is determined by dividing the water vapor transmission at a given relative humidity and temperature by the AA or ethanol transmission at the same relative humidity and temperature.

TABLE 12(DP-PP substrate)

^*ASTM F-739 Module (5 cm)²Area), 600cm³Flow rate per min

Watch 13(DP-PP base)

^*ASTM F-739 Module (5 cm)²Area), 600cm³Flow rate per min

As shown in table 12, the water vapor transmission rate generally increased with increasing RH for all three film samples. The water vapor transmission rate for the CA coating was significantly lower at all RH values tested. The water vapor transmission values of the coatings comprising blends of sPEEK and CA are closer to the values obtained for sPEEK coated films. As shown in table 13, the selectivity of all three membrane samples decreased with increasing RH. However, coatings comprising blends of sPEEK and CA provided better selectivity than sPEEK coatings under all RH conditions, and better selectivity than CA coated membranes under most conditions.

Thus, CA can be incorporated into sPEEK coatings (e.g., sPEEK-CA1:1) without having a major detrimental effect on WVT. The incorporation of CA into sPEEK coatings reduces contaminant crossover and increases the selectivity of the membrane for water transport when compared to coatings containing sPEEK alone.

Example 11 uptake ratio of Water and Water vapor adsorption

Samples of sPEEK, CA, sPEEK/CA, and Na-sPEEK/CA films were placed in liquid water and then patted dry and weighed to determine the equilibrium liquid water uptake in these samples at room temperature.

Watch 14 (Water uptake)

The water uptake observed for the sample comprising the blend of sPEEK and CA was not proportional to the "law of mixing", but had a slightly higher water uptake, which was closer to that of the sPEEK sample. This indicates that CA in the blend film does not prevent the sPEEK portion of the film from absorbing water to its maximum extent and, in fact, improves the overall uptake of the blend film. The neutralized Na-sPEEK with CA blend (when cast from acetone/water/ethanol) had a higher water uptake than the non-neutralized blend of sPEEK/CA, which was of the same order as the sPEEK sample.

The vapor sorption isotherms for the film materials shown in fig. 11 indicate a similar effect, indicating that the film comprising the blend of sPEEK and CA (1:1sPEEK: CA) has a water vapor uptake similar to the sPEEK polymer film alone. The vapor sorption test was completed using a gravimetric vapor sorption analyzer (Quantachrome), in which the samples were placed in an isothermal chamber, dried, and then exposed to air at a controlled relative humidity. The samples were equilibrated and the total moisture uptake at a given relative humidity and temperature was recorded. To generate the adsorption isotherm, a series of measurements were made at isothermal temperatures over a range of RH (i.e., 0% RH to about 100% RH). Desorption of water occurs more readily for films comprising blends of sPEEK and CA than for sPEEK films. sPEEK films tend to retain more water after desorption than sPEEK/CA films, which is closer to the CA film in the total desorption (fig. 12). Higher water vapor adsorption and greater desorption from blends comprising sPEEK and CA are beneficial in the following cases: water vapor must be absorbed and then desorbed in order for transport to occur across the membrane at a given humidity.

Example 12 humidity cycling

Membranes were made by coating selective layers comprising sPEEK and blends of sPEEK with CA (1:1) onto a microporous dry process substrate. The membrane was tested for leakage at the beginning of life (t ═ 0). The samples were placed in an environmental chamber (environmental chamber) where they were exposed to continuous humidity cycling (between 20% RH and 95% RH) at 50 ℃. Samples were tested for leaks every 100 cycles. Various other ERV membranes were also placed in the environmental chamber. All samples were at least in triplicate; seven samples of sPEEK and sPEEK/CA coated membranes were used. Table 15 shows the results at 45cm²Maximum leak rate measured for each sample at 3psi upstream pressure over the membrane area. An increased leak rate beyond the beginning of life leak rate indicates that damage to the membrane occurred during the humidity cycling test. Due to the semi-porous nature of paper-based ERV membranes, they show some leakage at the beginning of life.

Watch 15 (RH cycle of ERV film)

(-) indicates that the sample was removed from the chamber

It is evident from the RH cycling test that many commercially available ERV materials are not resistant to RH cycling. However, when used in ERV applications, such materials will typically be continuously exposed to varying RH conditions over the life of the material. sPEEK/CA coated membranes resist the RH cycle test. sPEEK coated films did show some leakage after RH cycling, indicating that sPEEK coated films are less robust to humidity cycling conditions than films coated with blends of sPEEK and CA. However, sPEEK leaks are orders of magnitude lower than many commercially available products. Without being bound to any particular theory, it is believed that the 'less swellable' CA strengthens sPEEK and prevents excessive swelling and dimensional instability that would otherwise lead to defects and failures over time under RH cycling conditions.

Example 13 neutralization of blends of sPEEK with CA to the sodium form

sPEEK is neutralized (i.e., sulfonic acid groups are proton exchanged to cations) due to degradation of CA in acid solutions as well as in sPEEK/CA film layers. To prepare a neutralized/exchanged Na-sPEEK/CA (1:1) coating solution, 2.5g of sPEEK and 2.5g of CA were dissolved in 80/20 acetone/water and the solution was made up to 90g (5.6% solids). Dropwise addition of 0.5M NaHCO₃Or NaOH until the pH is between about 5 and about 6. The final polymer solids content was about 5%. When the coating solution contained 2.5g of sPEEK, 0.42g of NaHCO was added₃。

Alternatively, the sPEEK may be treated with an excess of 0.1M NaOH. The sPEEK was soaked in 0.1M NaOH solution and rinsed with deionized water until the pH of the wash solution was neutral (i.e., pH about 7). The Na-sPEEK obtained is washed with deionized water and dried at 50 ℃. 2.5g of the resulting neutralized Na-sPEEK and 2.5g of CA were dissolved in a 72.5:27.5 acetone/water solution and the solution was made up to 100g (5% solids content).

Films cast from the neutralized/exchanged Na-sPEEK solution showed no signs of CA degradation. In membranes cast from these solutions, no leakage or long-term degradation of performance was observed and the WVT was substantially equal to sPEEK/CA membranes made from the protic form of sPEEK.

Example 14 Na-sPEEK and CA blend cast from ternary solvent solution

To reduce or minimize phase transitions and improve Na-sPEEK/CA coating on DP-PP substrates, a ternary solvent system may be used to formulate Na-sPEEK/CA coating solutions. The ternary solvent system may comprise acetone, water and ethanol. Using a differenceAcetone/water/ethanol ratio of 72/28(wt./wt.), sPEEK was about 63% DS, CA was about 39.7% acetyl content, and the average M of CA was_Nca. is about 50,000. In each sample coating solution, the sPEEK to CA (wt.: wt.) ratio was about 1:1 and the polymer solids content was about 4%. Use of 0.5M NaHCO₃To neutralize/exchange sPEEK to obtain Na-sPEEK/CA, as described elsewhere herein. Films were made by coating each sample solution onto a DP-PP substrate. The coating weight is about 0.5g/m²To about 1.5g/m²Within the range of (1). Films of coatings formulated from coating solutions containing 10 wt.% ethanol or less have some evidence of discontinuities or phase transformation-induced porosity. Except for the membranes made using the coating solution with 2% solid content, all membranes showed zero cross-leakage and zero EATR, indicating that a defect-free selective layer was cast on the DP-PP surface.

TABLE 16 (ternary solvent system)

Watch 17 (film property)

^*Discontinuous films or films with signs of turbidity, porosity or phase transition

^**Clear and homogeneous film without signs of haze

^***Dynamic WVT test, 33cm²Area, 6000cm³Flow rate per min, 50% RH in feed

sPEEK polymers have desirable properties for WVT membranes. However, dense films of sPEEK tend to be expensive and often have poor dimensional stability under wet conditions. Supporting a thin layer of such polymers on a microporous substrate can impart desirable mechanical properties to the resulting membrane as well as reduce the amount of expensive sPEEK polymers needed for a particular end use application. Membranes comprising microporous substrates coated with thin layers of sPEEK polymers were found to have desirable properties for ERV applications, including: a high WVT; low delivery of other chemicals (VOCs and odors); low air cross-over; and the ability to cast sPEEK polymers on higher performance substrates that are also flame retardant. However, under high humidity conditions, these polymers tend to swell, which may increase the permeability of VOCs and other undesirable chemicals, which reduces the selectivity of the membrane.

In seeking to further reduce the amount of sPEEK used in the coated film, sPEEK is blended with a cellulose derivative (which is less expensive) and the blended film is used as a coating. Surprisingly, it was found that films comprising certain blended polymer coatings exhibit water vapor permeability properties that are comparable to or even better than films comprising coatings made from sPEEK alone (even though the water vapor permeability of cellulose derivatives is typically significantly lower than the water vapor permeability of sPEEK polymers). This is particularly true when sPEEK is blended with CA, as shown in the examples and test results provided herein. Furthermore, the inclusion of CA in the blend tends to reduce swelling of the coating layer in the presence of high RH in the air stream in contact with the membrane. This reduction in swelling results in a significantly reduced transmission of VOCs through the membrane under high humidity conditions without significantly compromising water vapor transmission under all humidity conditions. The films with the blended polymer coating also exhibit improved stability under relative humidity cycling conditions relative to sPEEK coated films. Additional experiments have shown that blending CA or other cellulose derivatives with other highly water permeable polymers than sPEEK does not necessarily result in a polymer or film with desirable properties. It appears that it is not possible to predict the properties of the blended polymer based on the properties of the individual components in the blend. The combination of sPEEK polymers with CA appears to be particularly and unexpectedly advantageous.

ERV core

The ERV CORE may be of the type described in the applicant's international application No. PCT/CA2012/050918 entitled COUNTER-FLOW ENERGY RECOVERY Vehicle (ERV) CORE.

Fig. 13 shows a simplified isometric view of an embodiment of an ERV core comprising pleated membrane cylinders (200), the pleated membrane cylinders (200) comprising alternating layers of membranes (201) and gas flow channels between adjacent layers. The flow channel may comprise a passage over the core on the surface of the membrane and be sealed so that there is a flow of gas through the core from one face to the other without mixing of the two flows through the membrane. The airflow is directed through the pleated membrane cylinders 200 of the ERV core such that one side of each membrane layer is exposed to one airflow 210 and the opposite side of the membrane layer is exposed to the other airflow 220. In the illustrated embodiment, the gas is in a cross-flow configuration. Counter-flow, co-flow and other relative flow configurations may be used depending on the geometry of the ERV core and manifold arrangement. Due to the difference in heat or moisture between the two gas flows, the transport of heat and moisture takes place through the membrane. The flow of heat and moisture can occur in either direction through the membrane, depending on the conditions of the air flows 220 and 210. When stream 210 is cold and dry and stream 220 is warm and humid, heat and humidity transport will occur across the membrane to heat and humidify stream 210 before it exits the core at 211. The warm and humid stream 220 will thus be cooled and dehumidified as it passes through the core and exits at 221.

The perimeter of the pleated membrane cylinder 200 is sealed to prevent gas leakage between the perimeter of the pleated cylinder and the interior of the ERV housing (not shown in fig. 13). For example, gaskets or seals 202 and 203 may be disposed along the edges and top and bottom surfaces of the pleated membrane cylinder 200 so that, as long as in an ERV system, a seal will be created between the inlet and outlet to prevent short circuiting of gas between the streams.

FIG. 14 shows a simplified view of an ERV core 300 in an ERV system 340. The system 340 may include a fan and control mechanism to move air through the system in the direction indicated by the arrows in fig. 14. A seal is created around the periphery of the core. The ERV system is in contact between the air in the enclosed building space 350 and the outside environment. The seal allows airflow to be directed through the ERV core 300 as follows: the manner is such that incoming air 320 entering the building 350 passes on one side of the membrane layer in the core 300 and outgoing air 311 exiting the building 350 passes on the other side of the membrane layer in the core. If the outgoing air 311 is cold and dry and the incoming air 320 is warm and humid, heat and moisture transport will occur through the membrane in the core, so that the outgoing/exhausted air 310 will have gained heat and moisture, and the incoming air 321 entering the building 350 will have been cooled and dehumidified.

Method of testing

To accurately and consistently coat films on a laboratory scale, a mayer rod coater is used. This type of coating apparatus may also be referred to as Meyer bar, miter rod, Meyerrod, metering rod, coating rod, balanced rod, doctor rod, or metering rod coaters. In these types of rods, the steel wire is tightly wound around the rod. The gap spacing created between adjacent windings of wire will depend on the diameter of the wire used to wind the rod. In the coating device used in the examples herein, a wire-wound rod is placed on top of a substrate with a substantially constant downward pressure, and then a polymer solution is deposited by pipette onto the substrate surface in front of the rod. The linear actuator drives the rod across the substrate surface at a constant rate, spreading the coating on the substrate. The thickness of the wet coating deposited on the substrate surface will depend on the diameter of the wire used to wind the rod. The filament diameters used range from 0.05mm to 0.3mm, allowing controlled wet thin film deposition ranging from about 4 microns to about 24 microns. The coating settles by gravity to a thin film of substantially uniform wet thickness, after which the material is dried to remove the solvent and produce a coated substrate with consistent dry coating thickness and coating load. Further improvements in coating load can be obtained by varying the solids content, viscosity, density and surface tension properties of the solutions used. In the roll-to-roll process, a die or reverse gravure coating method is preferable.

To evaluate the air permeation or air crossover properties of the membrane materials in the examples herein, the membrane samples were sealed in a test apparatus. Pressurized air was applied to one side of the membrane and the air flow through the material was recorded. In a typical test, pressurized air is applied at 3psi or 20.7 kPa. In cubic centimeters per minute (cm)³Min) the cross flow rate through the test sample was recorded. This value can be determined by dividing by the applied pressure and the membrane area (45 cm in a typical test)²) Is converted into an air permeability value. Can be measured in cm³/min/cm²The air permeation was recorded as/kPa. Unless otherwise reported, the film samples had zero air crossover, indicating that there were substantially no defects in the coating layer of the film.

The Exhaust Air Transport Ratio (EATR) provides an indication of the amount of contaminant gas that may pass through the membrane material. Less than 5% would be desirable for this value, and more desirably less than 1% for it. Optimally, there is 0% contaminant gas transport through the material. Tests were developed to determine the EATR of the membrane. In this test, again, the membrane sample is placed in a testing apparatus that separates two sides of the membrane so that separate gas streams can be provided on opposite sides of the membrane. The module has a length of 33cm²Wherein the gas flow is directed in countercurrent directions on opposite sides of the membrane, the gas flows through 7 channels, each channel being about 16cm long, 1mm deep, and 3mm wide. On one side of the membrane, a pure nitrogen stream is passed over the surface of the membrane. On the other side of the membrane, the air stream passes over the membrane surface. The flow rates of the gases on each side of the membrane were equal in any given test, however, delivery was measured at two flow rates, 2000cm, for each sample³A/min (about 1.6m/s) and 500cm³Permin (about 0.4 m/s). At lower flow rates, the residence time of the gas flowing over the membrane surface in the module is longer and higher transport rates can be measured. Oxygen and nitrogen transport in this test is a measure of defects in the coating layer. Films having coatings substantially free of defects were found to be 2000cm³Min and 500cm³There should be zero EATR at both flow rates/min. The pressure difference between the two streams is maintained at zero so that only diffusive transport and no convective transport occurs across the membrane. An oxygen sensor was placed at the outlet of the nitrogen stream to measure the oxygen concentration. Since the concentration of oxygen in air is known, and the nitrogen flow does not contain oxygen at the inlet, the percentage of oxygen that diffuses through the membrane can be reported as:

EATR％＝{[C(O₂,1)]/[C(O₂,2)]}x 100

wherein C means oxygen (O)₂) Percent concentration at position 1 and position 2, where position 1 is at the outlet of the nitrogen side (measured by the sensor) and position 2 is at the inlet of the air side (measured at 20.9%).

A dynamic Water Vapor Transport Rate (WVTR) test procedure was developed that was designed to test membranes under conditions similar to those in which the membranes might be utilized. This Test device is similar to the devices described by p.gibon, c.kendrick, d.rivin, l.sicuranza, and m.charmchi, "An Automated Water Vapor Diffusion Test Method for Fabrics, amines, and Films," Journal of Industrial tests, volume 24, phase 4, page 322 & 345, month 4 1995 as dynamic moisture permeation tests (dynamic moisture permeation Test), and is also summarized in ASTM E298 and specifically in ASTM F2298. The membrane sample is sealed in a testing device having flow field channels on both sides of the membrane to distribute gas evenly over both surfaces of the sample, the gas being separated by the membrane. The flow rate, temperature and RH of each inlet gas flow can be controlled and the outlet temperature and RH of each gas flow can be measured. The gas is supplied and directed in counter-current flow over the opposite surface of the membrane. The effective area of the membrane in the test jig (test jigs) was 33cm². In a typical isothermal test, at 6000cm³A first gas stream (sweep stream) was supplied to the inlet on one side of the membrane at 50 ℃ and 0% RH/min (about 8 m/s). A second gas stream (feed stream) was supplied to the inlet on the other side of the membrane at 50 ℃ and 50% RH and at the same flow rate as the first gas. At the outletThe water content and temperature of the two streams were measured and recorded. For these values, the water delivery rate of the test sample was determined in units of mass per time (g/h). The results can also be reported as water flux by dividing by the membrane area over which transport has been in mass per area per time (kg/m)²H or in units of mol/m²Units of/s) occur. The permeability value can be measured in mass per area per time per partial vapor pressure difference (mol/m) by dividing the flux by the calculated average vapor pressure difference across the membrane within the test module²/s/Pa) and is typically reported in units of Gas Permeability (GPU), where 1GPU is 1 × 10^-6cm³(STP)cm^-2s^{- 1}cmHg^-1). The permeability is reported as the apparent permeability, without consideration of the concentration boundary layer associated with water vapor at the membrane surface. Due to the numerical range of the results, it was found most convenient to report the water delivery data as kg/m²Water flux values in units of/day. For tests in which the temperature and RH were not at standard test conditions (feed stream, at 50 ℃ and 50% RH), temperature and humidity were reported. In certain tests, membrane water vapor transport was measured with the feed stream at 25 ℃ and 50% RH. In other tests, the feed stream relative humidity was varied.

To measure the transport of 'contaminants' across the ERV membrane, Acetic Acid (AA) and ethanol were used as example VOC contaminants for the permeation test. The transmission method for measuring chemical transport in a membrane is improved from ASTM F-739: standard test methods for the permeation of liquids and gases through protective garment materials under continuous contact conditions. Quantitative analysis was performed using a TD-GC system.

The results are reported as the percentage of the contaminant concentration measured in the collection stream (collection stream) divided by the contaminant concentration in the supply stream according to the following equation:

wherein Q₁Is the flow velocity in the sweep flow (L/min); q₃Is the flow rate in the feed stream (L/min); c_x2Is the concentration of contaminant x (μ g/L) in the sweep stream; and C_x3Is the concentration of contaminant x (μ g/L) in the feed stream. The module used in this test is a standard module (manufactured by Pesce Lab Sales) for the ASTM F-739 test. At a diameter of 1 ", the module has an effective area of 0.785in²And 5cm². In each experiment, the gas was measured at 600cm³Min, supplied on either side of the membrane. The concentration of acetic acid in the feed stream is typically in the range of 100ppm to 200ppm, and the concentration of ethanol in the feed stream is typically in the range of 200ppm to 400 ppm.

The flame color test used was based on the UL-94HB horizontal burn test standard from Underwriters Laboratories, which was designed to determine the flammability of the material. Samples of the film were cut to 1.25cm x 12.5 cm. The sample is supported horizontally and then tilted longitudinally at an angle of 45 ° to the horizontal. A propane flame about one centimeter high was applied to the lower short edge of the tilted film sample. The flame was held to the sample until the flame spread to 2.5cm of the material. After 2.5cm of material was burned, the flame was removed and allowed to propagate across the material. The burning time and burning distance were recorded and the burning rate was determined in cm/s. The material passes the HB test if the material self-extinguishes before 10cm marking and the material has a burn rate of less than 0.125 cm/s.

Current membranes are particularly suitable for use in enthalpy exchangers (enthalpy exchangers), but may also be suitable for other applications involving the exchange of moisture and optionally heat between gas streams with little or no mixing of the gas streams through the membrane. Such potential applications include fuel cell humidifiers, gas drying, dehumidification, medical gas humidification, desalination and aircraft humidification, water filtration, gas separation and flue gas heat and water recovery.

The current film is preferably coated on only one surface of a thin layer with a water permeable polymer to give an anisotropic film as described above. However, films having different properties and water transport properties may be obtained by applying the coatings described herein on both sides of a substrate to provide a thin surface layer forming a water permeable polymer on both sides of the substrate.

Current membranes are preferably coated with a blended polymer comprising sPEEK. sPEEK belongs to the polyaryletherketone family of polymers and although sPEEK is preferred for current membranes, one skilled in the art will recognize that various polyaryletherketones can be sulfonated and used in a similar manner.

Interpretation of terms

Throughout the specification and claims, unless the context clearly requires otherwise:

"comprising," "comprising," and like terms should be interpreted in an inclusive sense as opposed to an exclusive and non-exhaustive sense; that is, in the meaning of "including, but not limited to";

"connected", "coupled", or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements may be physical, logical, or a combination thereof;

the words "herein," "above," "below," and similar import, when used in describing this specification, are to be construed as a whole and not as a specific part of this specification.

An "or" in reference to a list of two or more items, covering all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list;

the singular forms "a", "an", and "the" also include any appropriate plural reference.

Directional words such as "vertical," lateral, "" horizontal, "" upward, "" downward, "" forward, "" rearward, "" inward, "" outward, "" vertical, "" lateral, "" left, "" right, "" front, "" rear, "" top, "" bottom, "" below, "" above, "" below (under) … …, and the like for the purposes of this specification and any appended claims (where present), depend upon the particular orientation of the device being described and illustrated. The subject matter described herein may exhibit a variety of selectable orientations. Accordingly, these directional terms are not strictly defined and should not be narrowly construed.

When a component (e.g., a substrate, an assembly, a device, a manifold, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a "means") should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments described herein.

Specific examples of systems, methods, and devices have been described herein for illustrative purposes. These are merely examples. The techniques provided herein may be applied to systems other than the exemplary systems described above. Many variations, modifications, additions, omissions, and substitutions are possible in the practice of the present invention. The present invention includes variations to the described embodiments that will be apparent to the skilled addressee (skilleddress), including those obtained by: substitution of equivalent features, elements, and/or acts for those described; mixing and matching features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments described herein with features, elements and/or acts of other technologies; and/or omitting features, elements and/or acts from combinations of the described embodiments.

It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions and sub-combinations as may be reasonably inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims (39)

1. A water vapor transport membrane comprising a microporous substrate and a gas impermeable selective layer coated on a first surface of the substrate to form a substantially nonporous film thereon, the selective layer comprising sulfonated polyether ether ketone (sPEEK): Cellulose Acetate (CA) in a weight ratio of sPEEK to CA in the range of 7:3 to 2:3, wherein the CA has an acetyl content in the range of 20% to 62%, the sPEEK has a degree of sulfonation in the range of 23% to 100%, and the selective layer has a thickness of less than 5 microns.

2. A water vapor transport membrane according to claim 1, wherein the sPEEK comprises sPEEK in cationic form.

3. A water vapor transport membrane according to claim 2, wherein 80% to 100% of the sPEEK is in cationic form.

4. A water vapor transport membrane according to claim 3, wherein the cationic form is a sodium ion form.

5. A water vapor transport membrane according to any one of claims 1 to 4, wherein the degree of sulfonation of the sPEEK is between 60% ± 10% and 70% ± 10%.

6. A water vapor transport membrane according to any one of claims 1 to 4, wherein the coating load of the selective layer on the substrate is at 0.5g/m²To 2.5g/m²Within the range of (1).

7. A water vapor transport membrane according to any one of claims 1 to 4, wherein the thickness of the selective layer is 0.75 to 1.25 microns.

8. A water vapor transport membrane according to any one of claims 1 to 4, wherein the selective layer is sufficiently flexible to allow pleating of the membrane without breaking the selective layer.

9. A water vapor transport membrane according to any one of claims 1 to 4, wherein the water vapor transmission rate of the membrane is at least 9,000GPU at a temperature in the range of 25 ℃ to 50 ℃.

10. A water vapor transport membrane according to any one of claims 1 to 4, wherein the acetic acid crossover through the membrane is less than 1% at 25 ℃ and 50% relative humidity.

11. A water vapor transport membrane according to any one of claims 1 to 4, wherein the membrane selectivity for water vapor is greater than 50 compared to acetic acid at 25 ℃ and 50% relative humidity.

12. A water vapor transport membrane according to any one of claims 1 to 4, wherein the membrane is more permeable to water vapor than to Volatile Organic Compounds (VOCs) and other gases.

13. A water vapor transport membrane according to any one of claims 1 to 4, wherein the substrate is a polyolefin.

14. A water vapor transport membrane according to claim 13, wherein the polyolefin is dry processed and uniaxially or biaxially stretched.

15. A water vapor transport membrane according to any one of claims 1 to 4, wherein the porosity of the substrate is greater than 30% by volume.

16. A water vapor transport membrane according to claim 15, wherein the porosity of the substrate is in the range of 30% to 80% by volume.

17. A water vapor transport membrane according to any one of claims 1 to 4, wherein the substrate has a thickness of 5 to 40 microns.

18. A water vapor transport membrane according to any one of claims 1 to 4, wherein the average pore size of the substrate is in the range of 0.01 microns to 0.1 microns.

19. A method for manufacturing a water vapor transport membrane, the method comprising:

applying a coating solution or dispersion comprising sulfonated polyetheretherketone (sPEEK) and Cellulose Acetate (CA) to a first surface of a microporous substrate and allowing the coating solution or dispersion to dry to form a gas impermeable selective layer as a substantially nonporous film on the first surface of the substrate,

wherein the coating solution or dispersion comprises a sPEEK to CA weight ratio in the range of 7:3 to 2:3, the acetyl content of the CA is 20% to 62%, the sPEEK has a degree of sulfonation in the range of 23% to 100%; and is

Wherein the selective layer has a thickness of less than 5 microns.

20. The method of claim 19, further comprising proton exchanging the sulfonic acid groups of the sPEEK for cations.

21. The method of claim 20, wherein 80% to 100% of the sulfonic acid group protons of the sPEEK are exchanged for cations.

22. The method of claim 21, wherein the cation is sodium.

23. The method according to any one of claims 19 to 22, wherein the sPEEK has a degree of sulfonation between 60% ± 10% and 70% ± 10%.

24. The method of any one of claims 19 to 22, wherein the coating solution or dispersion has a solids content in the range of 2.5% to 10% by weight.

25. The method of any one of claims 19 to 22, wherein the coating solution or dispersion further comprises acetone/water, acetone/water/ethanol, Tetrahydrofuran (THF), THF/water, N-methyl-2-pyrrolidone (NMP), NMP/water, Dimethylformamide (DMF), DMF/water, dimethyl sulfoxide (DMSO), or DMSO/water.

26. The method according to any one of claims 19 to 22, wherein the coating load of the selective layer on the substrate is at 0.5g/m²To 2.5g/m²Within the range of (1).

27. The method of any one of claims 19 to 22, wherein the selective layer has a thickness of 0.75 to 1.25 microns.

28. The method of any one of claims 19 to 22, wherein the water vapor transmission rate of the membrane is at least 9,000GPU at a temperature in the range of 25 ℃ to 50 ℃.

29. The method of any one of claims 19 to 22, wherein the acetic acid crossing the membrane is less than 1% at 25 ℃ and 50% relative humidity.

30. The method of any one of claims 19 to 22, wherein the membrane selectivity to water vapor is greater than 50 compared to acetic acid at 25 ℃ and 50% relative humidity.

31. The method of any one of claims 19 to 22, wherein the membrane is more permeable to water vapor than to Volatile Organic Compounds (VOCs) and other gases.

32. The method of any one of claims 19 to 22, wherein the substrate is a polyolefin.

33. The method of claim 32, wherein the polyolefin is dry processed and uniaxially or biaxially stretched.

34. The method of any one of claims 19 to 22, wherein the porosity of the substrate is greater than 30% by volume.

35. The method of claim 34, wherein the porosity of the substrate is in the range of 30% to 80% by volume.

36. The method of any one of claims 19 to 22, wherein the substrate has a thickness of 5 to 40 microns.

37. The method of any one of claims 19 to 22, wherein the substrate has an average pore size in the range of 0.01 microns to 0.1 microns.

38. An Energy Recovery Ventilation (ERV) core comprising a pleated membrane cylinder comprising alternating layers of water vapor transport membranes according to any of claims 1 to 18 and gas flow channels between adjacent membrane layers.

39. An Energy Recovery Ventilation (ERV) system comprising an ERV core comprising a pleated membrane cylinder, wherein said membrane cylinder comprises alternating layers of water vapor transport membranes according to any of claims 1 to 18 and gas flow channels between adjacent membrane layers.

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